RESPIRATORY REGULATION DURING EXERCISE

1. CHAPTER 8 CHAPTER 8 RESPIRATORY REGULATION DURING EXERCISE RESPIRATORY REGULATION DURING EXERCISE

2. w Discover how your respiratory system regulates your breathing and gas exchange. (continued) Learning Objectives w Find out how the respiratory system brings oxygen to muscles and tissues and rids the body of excess carbon dioxide. w Learn the steps involved in respiration and gas exchange.

3. Learning Objectives w Examine how the respiratory stem functions during exercise and how it can limit physical performance. w Learn how the respiratory system maintains acid-base balance in the body. w Find out why this acid-base balance is important especially during physical performance.

4. External Respiration Pulmonary ventilation—inspiration and expiration Pulmonary diffusion—exchange of oxygen and carbon dioxide between the lungs and the blood

5. THE RESPIRATORY SYSTEM

6. INSPIRATION AND EXPIRATION

7. Pulmonary Diffusion w Replenishes blood's oxygen supply that has been depleted for oxidative energy production w Removes carbon dioxide from returning venous blood w Occurs across the thin respiratory membrane

8. THE RESPIRATORY MEMBRANE

9. Laws of Gases Dalton's Law: The total pressure of a mixture of gases equals the sum of the partial pressures of the individual gases in the mixture. Henry's Law: Gases dissolve in liquids in proportion to their partial pressures, depending on their solubilities in the specific fluids and depending on the temperature.

10. Partial Pressures of Air w Standard atmospheric pressure (at sea level) = 760 mmHg w Nitrogen (N2) is 79.04% of air; the partial pressure of nitrogen (PN2) = 600.7 mmHg w Oxygen (O2) is 20.93% of air; PO2 = 159.1 mmHg w Carbon dioxide (CO2) is 0.03%; PCO2 = 0.2 mmHg

11. Did You Know…? The solubility of a gas in blood and the temperature of blood are relatively constant. Differences in the partial pressures of gases in the aveoli and in the blood create a pressure gradient across the respiratory membrane. This difference in pressures leads to diffusion of gases across the respiratory membrane. The greater the pressure gradient, the more rapidly oxygen diffuses across it.

12. PO2 AND PCO2 IN BLOOD

13. Partial pressure (mmHg) % in Dry Alveolar Venous DiffusionGas dry air air air blood gradient Total 100.00 760.0 760 760 0 H2O 0.00 0.0 47 47 0 O2 20.93 159.1 104 40 64 CO2 0.03 0.2 40 45 5 N2 79.04 600.7 569 573 0 Partial Pressures of Respiratory Gases at Sea Level

14. w Gases diffuse along a pressure gradient, moving from an area of higher pressure to lower pressure. (continued) Key Points Pulmonary Diffusion w Pulmonary diffusion is the process by which gases are exchanged across the respiratory membrane in the aveoli to the blood and vice versa. w The amount of gas exchange depends on the partial pressure of each gas.

15. Key Points Pulmonary Diffusion w Oxygen diffusion capacity increases as you move from rest to exercise. w The pressure gradient for carbon dioxide exchange is less than for oxygen exchange, but carbon dioxide’s membrane solubility is 20 times greater than oxygen, so CO2 crosses the membrane easily.

16. Oxygen Transport w Hemoglobin concentration largely determines the oxygen-carrying capacity of blood. w Increased H+ (acidity) and temperature of a muscle allows more oxygen to be unloaded there. w Training affects oxygen transport in muscle.

17. OXYGEN-HEMOGLOBIN DISSOCIATION CURVE

18. Carbon Dioxide Transport w Dissolved in blood plasma (7% to 10%) w As bicarbonate ions resulting from the dissociation of bicarbonate ions (60% to 70%) w Bound to hemoglobin (carbaminohemoglobin) (20% to 33%)

19. - THE a-vO2 DIFF ACROSS THE MUSCLE

20. - The increase in a-vO2 diff during strenuous exercise reflects increased oxygen use by muscle cells. This use increases oxygen removal from arterial blood, resulting in a decreased venous oxygen concentration. Did You Know…?

21. Factors of Oxygen Uptake and Delivery 1. Oxygen content of blood 2. Amount of blood flow 3. Local conditions within the muscle

22. EXTERNAL AND INTERNAL RESPIRATION

23. w Hemoglobin is usually 98% saturated with oxygen which is higher than what our bodies require, so the blood's oxygen-carrying capacity seldom limits performance. (continued) Key Points External and Internal Respiration w Oxygen is largely transported in the blood bound to hemoglobin and in small amounts by dissolving in blood plasma. w Hemoglobin saturation decreases when PO2 or pH decreases, or if temperature increases. These factors increase oxygen unloading in a tissue that needs it.

24. - w The a-vO2 diff—difference in the oxygen content of arterial and venous blood—reflects the amount of oxygen taken up by the tissues. Key Points External and Internal Respiration w Carbon dioxide is transported in the blood as bicarbonate ion, in blood plasma or bound to hemoglobin. w Carbon dioxide exchange at the tissues is similar to oxygen exchange except that it leaves the muscles and enters the blood to be transported to the lungs for clearance.

25. Regulators of Pulmonary Ventilation at Rest w Higher brain centers w Chemical changes within the body w Chemoreceptors w Muscle mechanoreceptors w Hypothalamic input w Conscious control

26. RESPIRATORY REGULATION

27. Ventilation (VE) is the product of tidal volume (TV) and breathing frequency (f): VE = TV ´ f Pulmonary Ventilation

28. THE VENTILATORY RESPONSE TO EXERCISE

29. Breathing Problems During Exercise Dyspnea—shortness of breath. During exercise this is most often caused by inability to readjust the blood PCO2 and H+ due to poor conditioning of respiratory muscles. Hyperventilation—increase in ventilation that exceeds the metabolic need for oxygen. Voluntary hyperventilation reduces the ventilatory drive by increasing blood pH. Valsalva maneuver—a breathing technique to trap and pressurize air in the lungs; if held for an extending period, it can reduce cardiac output. This technique is often used during heavy lifts and can be dangerous.

30. Ventilation tends to match the rate of energy metabolism during mild steady-state activity. Both vary in proportion to the volume of oxygen consumed (VO2) and the volume of carbon dioxide produced by the body (VE). . . Did You Know…?

31. . . w The ratio between VE and VO2 in a given time frame . . . w At rest—VE/VO2 = 23 to 28 L of air breathed per L VO2 per minute . . . w At max exercise—VE/VO2 = 30 L of air per L VO2 per minute . . w Generally VE/VO2 remains relatively constant over a wide range of exercise levels Ventilatory Equivalent for Oxygen w Indicates breathing economy

32. . w When work rate exceeds 55% to 70% VO2max, energy must be derived from glycolysis. The Ventilatory Breakpoint w The point during intense exercise at which ventilation increases disproportionately to the oxygen consumption. w Glycolysis increases CO2 levels, which triggers a respiratory response and increased ventilation.

33. . . VE AND VO2 DURING EXERCISE

34. . . w Identified by noting an increase in VE/VO2 without an concomitant increase in the ventilatory equivalent for carbon dioxide (VE/VCO2) . . Anaerobic Threshold w Point during intense exercise at which metabolism becomes anaerobic w Reflects the lactate threshold under most conditions, though the relationship is not always exact

35. . . . . VE/VCO2 AND VE/VO2

36. w Ventilation increases upon exercise due to inspiratory stimulation from muscle activity which causes an increase in muscle temperature and chemical changes in the arterial blood (which further increase ventilation). (continued) Key Points Pulmonary Ventilation w The respiratory centers in the brain stem set the rate and depth of breathing. w Chemoreceptors respond to increases in CO2 and H+ concentrations or to decreases in blood oxygen levels by increasing respiration.

37. w Anaerobic threshold is identified as the point at which VE/VO2 shows a sudden increase, while VE/VCO2 stays stable. It generally reflects lactate threshold. . . . . Key Points Pulmonary Ventilation w Breathing problems associated with exercise include dyspnea, hyperventilation, and the Valsalva maneuver. w During mild, steady-state exercise, ventilation parallels oxygen uptake. w The ventilatory breakpoint is the point at which ventilation increases though oxygen consumption does not.

38. Respiratory Limitations to Performance w Respiratory muscles may use more than 15% of total oxygen consumed during heavy exercise and seem to be more resistant to fatigue during long-term activity than muscles of the extremities. w Pulmonary ventilation is usually not a limiting factor for performance, even during maximal effort, though it can limit performance in highly trained people. w Airway resistance and gas diffusion usually do not limit performance in normal healthy individuals, but abnormal or obstructive respiratory disorders can limit performance.

39. Respiratory Regulation of Acid-Base Balance w Excess H+ (decreased pH) impairs muscle contractility and ATP formation w The respiratory system helps regulate acid-base balance by increasing respiration when H+ levels rise. The increase in respiration allows more CO2 to be released in the blood (bound to bicarbonate) to be transported to the lungs for exhalation. w Whenever H+ levels begin to rise, from carbon dioxide or lactate accumulation, biocarbonate ions can buffer the H+ to prevent acidosis.

40. ARTERIAL BLOOD AND MUSCLE pH

41. RECOVERY AND BLOOD LACTATE LEVELS